Assembly principles of the human R2TP chaperone complex reveal the presence of R2T and R2P complexes.
Seraphim TV., Nano N., Cheung YWS., Aluksanasuwan S., Colleti C., Mao Y-Q., Bhandari V., Young G., Höll L., Phanse S., Gordiyenko Y., Southworth DR., Robinson CV., Thongboonkerd V., Gava LM., Borges JC., Babu M., Barbosa LRS., Ramos CHI., Kukura P., Houry WA.
R2TP is a highly conserved chaperone complex formed by two AAA+ ATPases, RUVBL1 and RUVBL2, that associate with PIH1D1 and RPAP3 proteins. R2TP acts in promoting macromolecular complex formation. Here, we establish the principles of R2TP assembly. Three distinct RUVBL1/2-based complexes are identified: R2TP, RUVBL1/2-RPAP3 (R2T), and RUVBL1/2-PIH1D1 (R2P). Interestingly, we find that PIH1D1 does not bind to RUVBL1/RUVBL2 in R2TP and does not function as a nucleotide exchange factor; instead, RPAP3 is found to be the central subunit coordinating R2TP architecture and linking PIH1D1 and RUVBL1/2. We also report that RPAP3 contains an intrinsically disordered N-terminal domain mediating interactions with substrates whose sequences are primarily enriched for Armadillo repeat domains and other helical-type domains. Our work provides a clear and consistent model of R2TP complex structure and gives important insights into how a chaperone machine concerned with assembly of folded proteins into multisubunit complexes might work.